A liner top packer is run as a part of a liner-hanger assembly to create a reliable liner-top seal between the host casing and the liner string. Additionally, the liner top packer can isolate formation pressures below the liner top from the casing above, can isolate treating pressures or acid work below the liner top from the casing, can isolate fluids while cement sets, can mitigate gas migration, and can isolate lost circulation zones. The liner top packer can also be used as a tieback completion or production packer. Therefore, the liner top packer serves a number of important and useful purposes.
In current techniques, hydraulics are used to set a liner top packer. For example, a liner top packer 30 as shown in FIG. 1A is hydraulically set in casing 10 with a hydraulic setting tool 20. The setting tool 20 has a bushing 22 disposed on a splined shaft 24 and threaded to a lock sub 31 of the packer 30. The setting tool 20 also includes hydraulic pistons 26 and a setting sleeve 28. The packer 30 includes a mandrel 32 coupled to the lock sub 31. Opposing slips 34 and cones 36 are disposed on the mandrel 32 on either side of a packing element 38.
During setting operations, the setting tool 20 is coupled by the bushing 22 to the lock sub 31 and the packer's mandrel 32 to run the packer 30 in the casing 10. When setting depth is reached, hydraulic pressure communicated in the setting tool 20 actuates the pistons 26, which pushes the setting sleeve 28 downward to compress the slips 34, the cones 36, and the packing element 38 and to set the packer 30. To build up pressure, a sub 23 threaded into the splined shaft 24 accepts a ball, which seals off the tubing to build pressure in the pistons 26. Rotation of the setting tool 20 then unthreads the bushing 22 from the lock sub 31 so the tool 20 can be retrieved.
As an alternative to the use of hydraulics, current techniques run and mechanically set a separate liner hanger below a liner top packer so a compression setting tool can then be used to set a liner top packer. For example, a liner top packer 30 as shown in FIG. 1B is coupled uphole of a separate liner hanger 35. The packer 30 has a packing element 38 disposed on the mandrel 32. The liner hanger 35 has slips 37a that are moved against cones 37b using a J-slot mechanism 39.
The packer 30 and liner hanger 35 are run in hole with the setting tool 20. When setting depth is reached, the liner hanger 35 is set in the casing 10 by operating the J-slot mechanism 39 and wedging the slips 37a with the cones 37b against the casing 10. At this point, rotation of the setting tool 20 unthreads the bushing 22 from the lock sub 31. The setting tool 20 is then lifted uphole inside the surrounding setting sleeve 28 until dogs 25 on the tool 20 bias outward beyond the distal end of the sleeve 28. Downhole movement of the setting tool 20 then engages the dogs 25 against the sleeve 28 so the sleeve 28 can be pushed against the packing element 38 on the packer 30 to set it against the casing 10. The setting tool 20 can then be removed.
Although these current techniques are successful, they may not be suitable for some implementations. For instance, using hydraulics downhole may be undesirable in implementations that have equipment that is pressure activated. Also, using a separate liner hanger adds additional cost to the assembly, which may be undesirable. These and other reasons may make alternative techniques more favorable for setting a liner top packer.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.